The present invention relates to a catalyst composition useful in the production of polyurethane containing isocyanurate, urethane, urea and/or biuret groups. The catalyst composition may also be used in the formation of a cellular polymer that is useful as thermal insulation.
Rigid foams containing urethane and predominantly isocyanurate groups (PIR foams) have been known for some time. Hydrocarbons, partially halogenated hydrocarbons and chemically generated carbon dioxide are normally used as blowing agents in the production of rigid foams.
Alkali metal carboxylates dissolved in polyols having a high OH value are typically used as catalysts in the production of rigid foams. Potassium 2-ethylhexanoate dissolved in ethylene or di-ethylene glycol, with a glycol concentration from 25 percent to 50 percent, is commonly used due to their activity and relative low cost. However, where relatively large quantities of these catalyst compositions are introduced in the production of rigid foams, the index is downshifted to such an extent that the property level of the foams is adversely affected. In particular, the dimensional stability of the foam products is seriously impaired, and the fire resistance of the polymer is reduced by the presence of urethane groups.
In U.S. Pat. No. 5,084,485, water is used to replace the high OH polyol as a solvent for an alkali carboxylate. However, this solution is not suitable for formulations employing a low level of water such as using a polyisocyanate in the formation of an insulation foam or high-density foam where the presence of a relatively large quantity of water is detrimental. In addition, the use of the catalyst composition described in U.S. Pat. No. 5,084,485 as a component for the formation of PIR foams results in undesirable properties. More particularly, a relatively large quantity of alkali metal carboxylates dissolved in at least 50 percent water used as catalysts in the production of rigid foams, as described in U.S. Pat. No. 5,084,485, results in a large amount of residual water and consequent carbon dioxide formation that adversely effects the property level of the foam product, e.g., higher friability, lower dimensional stability and thermal insulation factor due to the formation of carbon dioxide that acts as a blowing agent limiting the possibility to use other blowing agents such as hydrocarbons or hydrofluorocarbons, higher consumption of isocyanate and a decease in the ability to control the density of the foam.
Therefore, there exists a need for a catalyst composition including an alkali metal carboxylate or an alkaline earth metal carboxylate in a solution that can be employed in the production of a rigid foam which improves the property level, e.g., fire resistance and dimensional stability, of the rigid foam.